# FLUX.2 [klein] 4B Base LoRA API

> Text-to-image sa klein 4B Base na may LoRA, negative prompt at guidance, hanggang 50 hakbang

Bumubuo ng mga larawan mula sa prompt sa klein 4B Base na modelo, na naglalapat ng hanggang 3 LoRA sa pamamagitan ng `loras`. May `negative_prompt`, `guidance_scale` (default 5, 0 hanggang 20), 4 hanggang 50 inference na hakbang at setting na `acceleration`. Hanggang 4 na larawan bawat kahilingan, bilang jpeg, png o webp.

- Model id: `flux-2/klein/4b/base/lora`
- Made by: Black Forest Labs
- Category: Text to Image
- Output: image
- Price: $0.016 / megapixel (cheapest run $0.016 (16 API credits))
- Run: `POST https://api.doitong.com/v1/run/flux-2/klein/4b/base/lora`
- Quote: `POST https://api.doitong.com/v1/quote/flux-2/klein/4b/base/lora`
- Docs page: https://doitong.com/fil/developers/models/flux-2/klein/4b/base/lora

## Pricing

Price: **$0.016 / megapixel**. Billed per megapixel of output (width × height of every image). Each image is rounded up to a whole megapixel.

The full example input below costs $0.016 = 16 API credits (1 MP × 16 API credits).

Prices are the upstream price in USD, paid from the API balance in API credits (1000 API credits = 1 USD). `POST https://api.doitong.com/v1/quote/flux-2/klein/4b/base/lora` with the same JSON body returns the exact price for that input; the quote is exactly what a run charges. Invalid input is never charged and failed or canceled requests are refunded automatically.

## Input parameters

Send either the canonical name or the native field name (not both). Canonical names are the same across models.

| Parameter | Canonical name | Type | Required | Default | Allowed values / range | Description |
|---|---|---|---|---|---|---|
| `prompt` |  | string | yes |  |  | Prompt na gumagabay sa pagbuo ng larawan. |
| `negative_prompt` |  | string | no | `` |  | Negative prompt na tumutukoy sa content ng larawan na hindi isasama sa pamamagitan ng classifier-free guidance. |
| `guidance_scale` |  | number | no | `5` | 0 – 20 | Scale na inilalapat sa classifier-free guidance. |
| `seed` |  | integer \| null | no |  |  | Override ng seed ng pagbuo; kapag inalis ito, random na pumipili ng seed ang pagbuo. |
| `num_inference_steps` |  | integer | no | `28` | 4 – 50 | Bilang ng inference step na isasagawa. |
| `image_size` |  | object {width, height} \| enum (string) | no | `landscape_4_3` | `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | Mga sukat ng larawang binubuo. |
| `num_images` | `num_outputs` | integer | no | `1` | 1 – 4 | Bilang ng larawang hinihingi para sa pagbuo. |
| `acceleration` |  | enum (string) | no | `regular` | `none`, `regular`, `high` | Antas ng acceleration na inilalapat habang bumubuo ng larawan. |
| `enable_safety_checker` |  | boolean | no | `true` |  | Safety checking na nagbabalik ng mga itim na larawan kapalit ng mga larawang na-flag na unsafe. Pinapagana ng true ang checking; dini-disable ito ng false para lamang sa mga awtorisadong account, habang sinusuri pa rin ang mga kahilingang walang authorization. |
| `output_format` |  | enum (string) | no | `png` | `jpeg`, `png`, `webp` | File format ng resultang larawan. |
| `loras` |  | array of object {path, scale} | no | `[]` |  | Mga LoRA weight na ilalapat, hanggang 3 entry. |
| `loras[].path` |  | string | yes |  |  | Lokasyon ng LoRA weight, na tinukoy bilang URL, HuggingFace repository ID sa anyong owner/repo, o lokal na path. |
| `loras[].scale` |  | number | no | `1` | 0 – 4 | Scaling factor na inilalapat sa LoRA, mula 0.0 hanggang 4.0. |

## Example input

Required parameters only:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
}
```

A fuller example:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
}
```

## Run it

Set `DOITONG_API_KEY` to a key from https://doitong.com/developers/dashboard#keys. `?wait=20` returns the finished request in the same call when it is ready within 20 seconds; otherwise poll `GET /requests/{id}` (it also accepts `?wait=`), or pass `webhook_url`.

### curl

```bash
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.com/v1/run/flux-2/klein/4b/base/lora?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
  }'

# Still "queued" or "running"? Poll with the id from the response:
curl "https://api.doitong.com/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"
```

### JavaScript

```javascript
const API = "https://api.doitong.com/v1";
const headers = {
  "Authorization": "Bearer " + process.env.DOITONG_API_KEY,
  "Content-Type": "application/json",
};

// Run the model; wait up to 20 s for the finished result in the same call
let res = await fetch(API + "/run/flux-2/klein/4b/base/lora?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
  }),
});
let request = await res.json();
if (!res.ok) throw new Error(request.error.code + ": " + request.error.message);

// Not finished yet: long-poll until it is
while (request.status === "queued" || request.status === "running") {
  res = await fetch(API + "/requests/" + request.id + "?wait=20", { headers });
  request = await res.json();
}
if (request.status !== "succeeded") throw new Error(JSON.stringify(request.error));
console.log(request.outputs.map((o) => o.url), request.cost.credits + " API credits ($" + request.cost.usd + ")");
```

### Python

```python
import os
import requests

API = "https://api.doitong.com/v1"
headers = {"Authorization": "Bearer " + os.environ["DOITONG_API_KEY"]}

payload = {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/flux-2/klein/4b/base/lora", params={"wait": 20}, json=payload, headers=headers)
request = r.json()
if not r.ok:
    raise RuntimeError(request["error"]["code"] + ": " + request["error"]["message"])

# Not finished yet: long-poll until it is
while request["status"] in ("queued", "running"):
    request = requests.get(API + "/requests/" + request["id"], params={"wait": 20}, headers=headers).json()
if request["status"] != "succeeded":
    raise RuntimeError(request["error"])
print([o["url"] for o in request["outputs"]], request["cost"]["credits"], "API credits", "$" + request["cost"]["usd"])
```

### MCP

The MCP server at `https://api.doitong.com/v1/mcp` exposes the tools `search_models`, `get_model`, `quote`, `run`, `get_request`, `cancel_request`, `list_requests`, `create_upload` and `get_account`. A `run` call for this model:

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "run",
    "arguments": {
      "model_id": "flux-2/klein/4b/base/lora",
      "input": {
        "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
      },
      "wait_seconds": 20
    }
  }
}
```

## Response

Every call returns a request object. `status` is one of `queued`, `running`, `succeeded`, `failed`, `canceled`. `outputs` lists the generated files with URLs on our storage (kept forever, or 7 days with `?storage=temporary`; `storage` says which); `output` is the model's own result object with the same URLs.

```json
{
  "id": "req_8k2m4q7x1z9c3v5b6n0p2r4t",
  "object": "request",
  "model": "flux-2/klein/4b/base/lora",
  "status": "succeeded",
  "created_at": "2026-10-20T12:00:00Z",
  "started_at": "2026-10-20T12:00:02Z",
  "completed_at": "2026-10-20T12:00:09Z",
  "queue_position": null,
  "cost": {
    "credits": 16,
    "usd": "0.016",
    "charged": 16,
    "refunded": 0
  },
  "input": {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field"
  },
  "output": {
    "images": [
      {
        "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
        "content_type": "image/jpeg",
        "file_name": "0-output.jpeg",
        "file_size": 1843200,
        "width": 1024,
        "height": 768
      }
    ],
    "timings": {},
    "seed": 42,
    "has_nsfw_concepts": [
      false
    ],
    "prompt": "string"
  },
  "outputs": [
    {
      "type": "image",
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_size": 1843200,
      "width": 1024,
      "height": 768,
      "stored": true
    }
  ],
  "error": null,
  "metrics": {
    "inference_seconds": 6.8
  },
  "urls": {
    "self": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t",
    "cancel": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t/cancel"
  }
}
```

### Output fields (`output`)

| Field | Type | Description |
|---|---|---|
| `images` | array of object {url, content_type, file_name, file_size, width, height} | Mga larawang ginawa ng modelo. |
| `timings` | object |  |
| `seed` | integer | Seed para sa pagbuo ng larawan, kasama ang random na napiling value kung walang seed sa input; kung hindi, inuulit nito ang ibinigay na value. |
| `has_nsfw_concepts` | array of boolean | Nagsasaad kung may mga konseptong NSFW sa nabuong mga larawan. |
| `prompt` | string | Prompt na ginagamit sa pagbuo ng larawan. |

## Related models

- [FLUX.2 \[klein\] 4B LoRA](https://doitong.com/developers/models/flux-2/klein/4b/lora.md) (`flux-2/klein/4b/lora`): $0.01 / megapixel
- [FLUX.2 \[klein\] 9B Base LoRA](https://doitong.com/developers/models/flux-2/klein/9b/base/lora.md) (`flux-2/klein/9b/base/lora`): $0.02 / megapixel
- [FLUX.2 \[klein\] 9B LoRA](https://doitong.com/developers/models/flux-2/klein/9b/lora.md) (`flux-2/klein/9b/lora`): $0.015 / megapixel
- [FLUX.2 \[klein\] 4B Base LoRA · Edit](https://doitong.com/developers/models/flux-2/klein/4b/base/edit/lora.md) (`flux-2/klein/4b/base/edit/lora`): $0.016 / megapixel
- [FLUX.2 \[klein\] 4B LoRA · Edit](https://doitong.com/developers/models/flux-2/klein/4b/edit/lora.md) (`flux-2/klein/4b/edit/lora`): $0.01 / megapixel
- [FLUX.2 \[klein\] 9B Base LoRA · Edit](https://doitong.com/developers/models/flux-2/klein/9b/base/edit/lora.md) (`flux-2/klein/9b/base/edit/lora`): $0.02 / megapixel
- [FLUX.2 \[klein\] 9B LoRA · Edit](https://doitong.com/developers/models/flux-2/klein/9b/edit/lora.md) (`flux-2/klein/9b/edit/lora`): $0.015 / megapixel
- [FLUX.1 \[dev\]](https://doitong.com/developers/models/flux/dev.md) (`flux/dev`): $0.025 / megapixel

## Links

- HTML page: https://doitong.com/developers/models/flux-2/klein/4b/base/lora
- All models and guides for AI agents: https://doitong.com/developers/llms.txt
- OpenAPI 3.1 with this model's typed request body: https://doitong.com/developers/openapi.json?model=flux-2/klein/4b/base/lora
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/flux-2/klein/4b/base/lora